1. Field of Invention
This invention relates to a method for treating via sidewalls, and more particularly to a method of using hydrogen plasma to treat organic spin-on-glass (SOG) via sidewalls in a manufacturing process of inter-metal dielectric semiconductor devices (IMD). The invention also includes a semiconductor device resulting from this method.
2. Description of Related Art
In conventional manufacturing processes for semiconductors, spin-on-glass is a fairly simple planarization technique. The main constituent of commonly used SOG is either a silicate or a siloxane. For a siloxane SOG, owing to the presence of organic functional groups, for example, methyl(CH.sub.3) or benzyl(C.sub.6 H.sub.5) groups from which the organicity for the SOG is derived, resistance against cracking of the SOG layer is very much improved, especially after the expulsion of residual solvent from the SOG layer through a heat treatment process (also known as "curing"). However, in practical applications, residual solvent and moisture can easily be retained leading to out-gassing in subsequent processes. For example, no matter whether an etched or non-etched process is used in the fabrication of IMD, subsequent heat treatment in the formation of aluminium or tungsten plugs will generate out-gassing. If the out-gassing from the SOG layer happens to be along the sidewalls of the vias, then electrical potential will be adversely affected by the change because of the increase in via resistance and poor connection with the metallic interconnects.
FIGS. 1A through 1D are cross-sectional views showing the progression of steps in a conventional treatment method for via sidewalls. Referring to FIG. 1A, in the manufacturing process for an inter-metal dielectric layer of a semiconductor, a liner oxide layer 104 is first deposited over a substrate 10 with metallic wires 102 already formed thereon. Then, an organic SOG layer 106 is deposited over the liner oxide layer 104, and making use of its good gap-filling ability, planarization of the area is achieved. Subsequently, a partial etching back processing of the SOG layer 106 may be performed to obtain a better planarized surface, or the partial etching back processing may be eliminated to save the corresponding production cost. Thereafter, a second oxide layer 108 is deposited above the SOG layer to form the whole inter-metal dielectric layer and a cross-sectional view as shown in FIG. 1B is obtained. The SOG layer 106 can be either fluidic or non-fluidic and a chemical-mechanical polishing operation can be further applied to obtain a better global planarization for the second oxide layer 108.
Next, via holes 110 are formed by suitable applications of photolithographic and etching processes. For example, etching can be carried out using an oxygen plasma treatment 112 and a wet etching removal method, and a cross-section as shown in FIG. 1C finally can be obtained. Thereafter, referring to FIG. 1D, tungsten or aluminium plug material 114 is used to fill up the via holes 110. However, owing to the out-gassing along the sidewalls of the via holes 110, defective portions 116 are formed in the via holes 110 and so a functionally inferior semiconductor product is obtained.